/**
 * 接口继承
 * 案例:2D模型、3D模型
 */
interface Point2D{
    x:number,
    y:number
}
interface Point3D extends Point2D{
    z:number
}

let p1:Point2D={x:34,y:23}
let p2:Point3D={x:34,y:23,z:56}